1. Field of the Invention
This invention relates generally to oilfield downhole tools and more particularly to modular drilling assemblies utilized for drilling wellbores in which electrical power and data are transferred between different modules and between rotating and non-rotating sections of the drilling assembly.
2. Description of the Related Art
To obtain hydrocarbons such as oil and gas, boreholes or wellbores are drilled by rotating a drill bit attached to the bottom of a drilling assembly (also referred to herein as a “Bottom Hole Assembly” or (“BHA”). The drilling assembly is attached to the bottom of a tubing or tubular string, which is usually either a jointed rigid pipe (or “drill pipe”) or a relatively flexible spoolable tubing commonly referred to in the art as “coiled tubing.” The string comprising the tubing and the drilling assembly is usually referred to as the “drill string.” When jointed pipe is utilized as the tubing, the drill bit is rotated by rotating the jointed pipe from the surface and/or by a mud motor contained in the drilling assembly. In the case of a coiled tubing, the drill bit is rotated by the mud motor. During drilling, a drilling fluid (also referred to as the “mud”) is supplied under pressure into the tubing. The drilling fluid passes through the drilling assembly and then discharges at the drill bit bottom. The drilling fluid provides lubrication to the drill bit and carries to the surface rock pieces disintegrated by the drill bit in drilling the wellbore via an annulus between the drill string and the wellbore wall. The mud motor is rotated by the drilling fluid passing through the drilling assembly. A drive shaft connected to the motor and the drill bit rotates the drill bit.
A substantial proportion of the current drilling activity involves drilling of deviated and horizontal wellbores to more fully exploit hydrocarbon reservoirs. Such boreholes can have relatively complex well profiles that may include contoured sections. To drill such complex boreholes, drilling assemblies are utilized that include steering assemblies and a suite of tools and devices that require power and signal/data exchange. Conventional power/data transmission systems for such drilling assemblies often restrict placement of certain tools due to difficulties in transferring power or data across individual drilling assembly components such as a drilling motor.
The present invention addresses the need for systems, devices and methods for efficiently transferring power and/or data between modules that make up a BHA.